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Repurpose a Road-Kill Auto Head Lamp - Help!

whiteoutage

Jul 20, 2017
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The circuit board(not pictured) was damaged. Would like to use as a work light in my garage? Can I just hook up a 12V power supply directly to the LEDs(second picture).
I did test them and there are six LEDs in pairs of two. Don't have a proper power supply so applied 5V with my old phone charger and all six LEDs lite dimly when I bridge the three negative posts on the connector together. When LED 1,2,3 are powered individually the pairs light with same brightness when bridging them.
Then, with a retired 6.8V camcorder PS the same results but with very bright lights. /Then again with a 12V PS - even still brighter. Tests were only for a second or two as I am afraid I will blow them up bypassing what may possibly be called the driver board (please forgive, i'm just an electronics knob who seams to fry LEDs far too often).
The heat sinks are huge so will those prevent them from blowing or do I need to add resistor(s), more circuitry somehow?
 

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Harald Kapp

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LEDs can't be used on a voltage source directly without current limiting (got a question about driving LEDs?). Thisis, I assume, what the driver board did. You can use the LEDs with added proper current limiting. A simple resistor may suffice, see the link in parentheses above. You will have to know the allowed current to chose the correct resistor though.
The heat sinks are huge so will those prevent them from blowing
No.
 

whiteoutage

Jul 20, 2017
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Thank you Harold, and thank you Steve for the informative article. I should be able to take it from there. Guess I'd heard about current limiting before but sometimes, for us hard headed types, it takes a project to iron in the concept. :rolleyes:
Still, it would be cool to know how all of you would repurpose this very cool car headlight (minus hosed driver board) into a useable work light, emergency light, etc, etc. What you'd do with it, how you'd wire it up?
Also, the lamp was encased in a protective outer shell that was nearly impossible to remove without hacking it up really good. I may just reuse cover as is (beat up/pounded/smashed/sawed/drilled/ripped) to protect the work light, but am thinking of designing a case for it also. So any ideas on giving the lamp a cover/protection/decor, etc. would also be appreciated!?

Happy Holidays to all the Great Electronics Point Advisors(the best) and of course to so many of the knowledgeable, helpful Members!! Guess I have to stop the EP references. Maker Pro is a cooler title anyhow - LOVE IT.
 
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whiteoutage

Jul 20, 2017
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LEDs can't be used on a voltage source directly without current limiting (got a question about driving LEDs?). Thisis, I assume, what the driver board did. You can use the LEDs with added proper current limiting. A simple resistor may suffice, see the link in parentheses above. You will have to know the allowed current to chose the correct resistor though.

No.
Here are some pictures of the damaged LED driver board. Looks like there are only two affected components, and the extracted capacitor tests good. That leave a mystery component. The car accident jettisoned the lamp assembly leaving behind the cord with missing piece, and in the process ripped out or lifted five solder pads. I soldered the bottom right pad back together.
After further thought, the missing bottom piece may actually be two parts (power post, and a three legged component).
Any ideas what the lower part(s) may be?
 

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whiteoutage

Jul 20, 2017
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Not sure what amperage these LEDs amperage specification are but no matter what voltage I applied to them they take about 5.5V so with a cheap class two 6V 1A wall wart I experimented with several high wattage resistors. With no resistor at all they only suck up 1A so this lamp is definitely not an auto's main head lights, and sure enough the stamped part number say they are DRL(daytime running lights). So 5.5W is max output. To be safe I will run them at half that or about 3W. Not the power I was expecting (35W is average headlamp rating). Will just slap them back in the beat up case with some used 2S 18650s & tape it up. At least lamp should make a good garage beater flashlight.
 

whiteoutage

Jul 20, 2017
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Found a little better power supply. A switch mode 6V @ 2A. Without a resistor the lamp draws 2A or 11W. With a 2 ohm two watt resistor pulls .60A, or double the previous 1A wall wart. Resistor only got warm, not hot after half an hour - lamp heatsink also just a little warm(seams like .6A would make a good high setting). Wonder if I had a 4A adapter if lamp would then suck 22W, and with an unloaded battery maybe it'd pull 8A or 44W or higher, and blow up everything?
 
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Harald Kapp

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Lacking the specs or a datasheet of the LEDs it's mostly guesswork and trial and error. If it works o.k. for you at 0.6 A, use it in this setup.
 

whiteoutage

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Lacking the specs or a datasheet of the LEDs it's mostly guesswork and trial and error. If it works o.k. for you at 0.6 A, use it in this setup.
Trial and error - story of my life.:rolleyes:I may be slow but once I understand something it tends to stick with me (ihope).
With a 2S battery configuration I'll do same trial/error to get a safe current for LEDs. This time I'll use the magic formula from Steve's dissertation: (R = (V - Vf) / I) so start out with an (8-5.75V)/.5=5.50 Ohm resistor rated at 2.75V*.5A=1.37 Watts.
This should give about 8V*.5A or 4 Watts power when battery is full, and 5V*.4A(guess)=2W when battery is empty.

Thank you Harald!
 
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whiteoutage

Jul 20, 2017
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Had an immediate basement flashlight need so back to the adapter configuration. May have to make a hot swappable AC/DC mod.
 
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